1. Field of the Invention
The present invention relates to a recording medium suitable for recording by use of ink, such as recording by felt pens, fountain pens, pen plotters, ink jet recording devices or the like, and particularly, to a recording medium excellent in the ink absorbency and the colorfulness, definition and gloss of recorded images, and to an image formation process for obtaining recorded images of high image quality.
2. Description of the Related Art
Conventionally, recording media used for recording by use of ink, for example, writing by fountain pens, felt pens, ball point pens, etc. or recording by pen plotters, ink jet recording devices, etc. include ordinary paper such as high quality paper, bond paper and writing paper, or coated paper such as art paper and cast coated paper.
However, along the recent progress in recording devices such as ink jet recording devices and pen plotters, desirable recording performances have not been achieved by the above conventional recording media.
Since a high speed recording and a multi-color recording are carried out in recording processes as mentioned above to levels that can not be compared with conventional processes, the ink absorbency, the coloring performance required when plural kinds of ink have been deposited on the same place, and colorfulness, etc. have not reached satisfactory levels in the conventional recording media.
To solve these probelems, there has been hitherto proposed a number of coated paper, typified by ink jet paper, having a porous ink absorbing layer on the surface of a substrate. For example, recently, Japanese Patent Laid-open Publication No. 214989/1985 discloses a sheet provided on a substrate with a porous resin ink absorbing layer. This ink absorbing layer is a porous layer having minute pores or fissures in the interior, whereby the ink absorption rate is said to be improved.
It is possible to improve the ink absorbency to a certain extent by providing such a porous ink absorbing layer, but because the absorbing layer is porous, a recording medium tends to have a light diffusion property to make it impossible to obtain sharp recorded images having high optical density and glossy images also.
There is also a disadvantage that the recorded image has inferior resistance or preservability such as water resistance and abrasion resistance, because recorded images are viewed from one side of an ink recording face and thus the recording medium is constructed such that a recording agent is retained on the surface of the absorbing layer as much as possible.
European patent application No. 0049049 proposes a liquid-absorbent media constituted of a liquid-absorbent layer and a liquid-permeable layer in combination to improve surface characteristics of a substrate for pen plotters. The media are mainly characterized by their transparency, but the media are not suitable for recording apparatuses or recording methods requiring especially rapid ink-drying property since the inherent liquid absorbency of the underlayer is retarded by the surface layer having a higher liquid absorbency, even though the media have surface characteristics improved in a certain degree.
As a means for solving such problems, there are known, for example, a recording medium disclosed in Japanese Patent Laid-open Publications No. 136480/1983 and No. 136481/1983. This recording medium comprises an ink receiving layer provided on a substrate, mainly composed of a pigment having the refractive index of 1.58 or less, and is of such a type that the recorded images are viewed from the side of the substrate. In this recording system, performances such as water resistance at the viewing side have been well satisfied. However, although the whiteness is increased by the employment of a large amount of pigment for enhancing the whiteness of the ink receiving layer, the ink deposited tends to be adsorbed by the pigment to lessen the amount of the ink reaching the interface between the ink receiving layer and the substrate, and thus there are disadvantages such that the image density can not be made sufficiently high at the viewing side and also the colorfulness, the definition, etc. are inferior.
Recently, as the recording practiced by use of ink jet recording devices, pen plotters, etc. becomes higher in fidelity, there are increasing demands for the recording media that may have greatly improved recording performances. In other words, it has become necessary to provide recording media markedly superior to the conventional media in all the traits of ink absorbency, the coloring performance of a recording agent, the image quality of recorded images, the definition, the colorfulness, the density of recorded images, the glossiness, the water resistance, the light-resistance, etc. At present, however, no recording media have been obtained that can satisfy all of these recording performances simultaneously.